If you are planning to work in Singapore on an Employment Pass instead of as a citizen, you won't need to contribute to CPF. You may want to look up the EP section on Ministry of Manpower and send an enquiry to the office. You can still apply for EP even if you were born in Singapore. You do need to fill out extra personal particulars along with the EP application.
P.S. I am not an expat of Singapore citizenship. Just saw this part when I was doing my application. So please verify this with the authority.